Recently, a device for driving an elevator with a new system has been developed, and its patent application has been filed (for example, refer to Japanese Patent Unexamined Publication No. 2003-252554).
Referring to FIG. 10, in this device 9 for driving an elevator, an elevator rope 92, one end of which is provided with an elevator cage 90 and the other end is provided with a balance weight 91, is entrained about a sheave 93, and the elevator cage 90 can be moved up and down by pressing a belt 95 for driving an elevator stretched over a plurality of flat pulleys 94, into contact with an arcuate region of an elevator rope 92 wound around the sheave 93, and allowing one of the plurality of flat pulleys 94 to be rotatably driven by a motor.
The device for driving an elevator with this system has the merit of employing a relatively small motor as the rotary driving source of the belt 95.
However, in the device 9 for driving an elevator, if oil or water adheres to the belt 95 or the flat pulleys 94 over which the belt 95 is stretched, the coefficient of friction between them is lowered, and hence the rest retaining capability thereof is lowered. When the rest retaining capability is extremely lowered, it is impossible to stop the rotation of the sheave 93. This results in a considerably unfavorable condition where the elevator cage cannot retain its stopped state.